My suggestion is that the Nether, End, Mining, Twilight Forest worlds be reset monthly.
This suggestion comes from another server that have implemented it and it works well.
The purpose of resetting the worlds is so that players can use a new mining world and not have to travel for loads of blocks because they've mined their immediate area and beyond. The Twilight Forest needs to be reset most of all. Right now, players that've joined recently won't be able to collect any materials without killing the Naga.
The cost of this idea is pretty low. You would need to set a day which you reset the world (i.e first or last day of the month), advertise this day and then action it. I think that for the first 2 months, refunds might be offered on a case-by-case basis (haven't been on to see the advertisement etc) after this, I don't believe that refunds should be offered to players losing items like quarries due to the reset of the world as it should be a known event in the server's calendar. Im sure that if you have any programmers in your arsenal of people then creating a script to reset the world won't be difficult.